The effect of surgical removal of either the periphery or afferent input of one or both of the two cell populations of the chick ciliary ganglion on the subsequent development of synaptic connections will be investigated utilizing both electrophysiological and ultrastructural techniques. The ability of the periphery to influence neural specificity and synaptic connectivity of these ganglion cells will thereby be determined. The dependence of specific cellular characteristics such as axon diameter, the formation of myelin, the development of calyces, dendritic sprouting, specializations necessary for chemical and electrical transmission, on either the periphery or afferent input will also be determined. By selective denervation, attempts will be made to cause reinnervation of one type of ganglion cell by the wrong type of preganglionic fiber, and resulting alterations in synaptic function and ganglion cell characteristics will be studied. The ability of nerves to trophically influence the nature of the postsynaptic acetylcholine receptors will be determined by innervating the aneurogenic part of the frog sartorius by either normal sartorius nerves or preganglionic autonomic fibers of the vagus nerve. The pharmacology of the resulting synaptic receptors as well as their reversal potentials will be studied.